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FWIW: I have used old motor oil in a 9 X 12 baking pan as an effective
artifical horizon. It is very black and worked quite well if a little messy.

Vic
________________________________________________________

Victor Fraenckel - The Windman                 vfraenc1@nycap.rr.com
KC2GUI                                                      www.windsway.com

      Home of the WindReader Electronic Theodolite
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"Victory at all costs, victory in spite of all terror, victory however long
and hard the road may be; for without victory there is no survival."
- Winston [Leonard Spencer] Churchill (1874 - 1965)

Dost thou not know, my son, with how little wisdom the world is governed?
-Count Oxenstierna (ca 1620) to the young King Gustavus Adolphus

----- Original Message -----
From: "Robert Eno" 
To: 
Sent: Friday, July 11, 2003 7:45 PM
Subject: Re: Arificial Horizons and Tea


| Eno responds,
|
| My job, among other things, involves the management and disposal of
| hazardous waste. Mercury is right up there with the nasties; worse than
PCBs
| and worse than many other substances. Very useful stuff but hazardous when
| mishandled.
|
| I can't cite the literature but some time ago, there was a study conducted
| on the health of chemistry teachers and anyone else who spent most of
their
| working days in chemistry labs. It was found that these professions had
much
| higher incidences of minimata disease -- essentially, short circuiting of
| the nervous system -- and that this was caused by the slow volatilization
of
| mercury trapped in the sink drains and cracks in the floor. Most students,
| when confronted with broken thermometers, would simply hide their sins by
| flushing the mercury down the drain (guilty as charged), after which it
| would remain in the sink trap and slowly poison the lab teacher.
|
| Mercury is not to be trifled with. In fact it should be avoided. The more

| you handle it, the more long term risks you take with your health. Stay
| clear of it. It is simply not worth the risk when there are far superior
| artificial horizons available.
|
| I have used them all: mercury, water, oil, etc. etc. and my vote is for
the
| flat black glass artificial horizon. That it is not self-leveling like
| mercury or tea, is merely an inconvenience; not a serious impediment to
| accurate position fixing. I much prefer a glass horizon. Mercury, tea, oil
| and other liquids are simply a pain in the a---. Actually, I prefer a
bubble
| horizon. The old C.Plath is the best ever.
|
| As for mercury amalgams, the jury is not out yet. There are many
conflicting
| reports and opinions, however, the overall consensus -- based on data from
| the millions of unwitting guinea pigs (like me) -- seems to be that the
| mercury amalgams in our fillings do not present a serious risk. They have
| been used for close to a hundred years and there does not seem to be any
| evidence of damage to the nervous systems of people with bad teeth.
|
| My two bits' worth.
|
|
| Robert Eno
|
| >
| > I suspect that it may be less lethal than John Kabel implies.
| >
| > I base this opinion on my childhood at school, where I sat for physics
| > classes at a laboratory bench. Every hollow and cranny in the wooden
| > surface of that bench would contain droplets of mercury. When the lesson
| > became boring, we would do our best to fish them out with a pencil, to
| > collect enough to coalesce into a blob that was big enough to flick at
our
| > friends in the row in front.
| >
| > Our reversing-switches would involve electrodes that dipped into open
| pools
| > of mercury, We would make barometers that dipped into similar open
pools.
| >
| > Later, at university, we found a similar environment. We would use
mercury
| > in pint quantities for diffusion-pumps in high-vacuum systems.
| >
| > I suspect many physics students from my generation, the world over,
could
| > tell a similar story.
| >
| > Were we risking our lives? It didn't seems so at the time. I haven't
| > collected mortality statistics. Were we risking brain damage? Perhaps
| > that's starting to show, now...
| >
| > Now we have our teeth stuffed with amalgam. Does the amalgamation remove
| > the toxicity? I wonder.
| >
| > Somehow I doubt that taking sextant altitudes by exposing for a short
time
| > a small pool of mercury, out in the open, where any vapour could blow
| away,
| > presents a comparable hazard. But I am quite prepared to be convinced
| > otherwise, if any real evidence exists. Is John Kabel being
over-alarmist
| > about the danger? Am I being over-casual?
| >
| > In other respects, mercury must be the ideal artificial horizon. There's
| > room for a simple design in plastic for a shallow pool with a sealing
lid,
| > from which the mercury would never need to be removed, with a rim
intended
| > to trap any overspill, designed with a tripod base. This would be
handier
| > than the equipment the old explorers had to handle, in which mercury had
| to
| > be transferred between a tray and an iron storage vessel with a
screw-cap.
| >
| > But how available is mercury today? Are there regulations that prevent
you
| > and me from acquiring enough mercury to do the job? Do we have to
collect
| > antique barometers to do so?
| >
| > I'm not convinced about the virtues of floating a solid mirror on a
| > disc-raft on liquid. The liquid and the solid would need to have a
| > repulsive surface tension between them to ensure blobs wouldn't gather
up
| > the sides of the raft. That surface tension would require to be exactly
| > even around the edges of the disc or the raft would be unbalanced. How
| > would one prevent the raft from nearing the edges of the container,
which
| > would unbalance the surface-tension forces or give rise to friction
which
| > would constrain the self-levelling? There are serious problems here
which
| > would need resolving.
| >
| > George Huxtable.
| >
| >
| > ================================================================
| > contact George Huxtable by email at george@huxtable.u-net.com, by phone
at
| > 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
| > Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
| > ================================================================
| >
| >

   

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